In recent years, semiconductor light emitting elements such as light emitting diodes (LED) having high energy efficiency in light emission have been used in various fields, and various apparatuses utilizing such semiconductor light emitting elements have been developed. Emitting light with large currents or efficiently emitting light with reflectors or the like, in particular, semiconductor light emitting elements have drawn attention toward their use as lighting substituting for conventional fluorescent lamps or incandescent lamps, and techniques intended to resolve a problem of heat generated by light emission have been proposed to date.
For example, there is proposed a light emitting device having heat dissipation properties improved as compared to conventional devices and being capable of efficiently extracting light from a semiconductor light emitting element to the outside (see Patent Document 1, for example). In the light emitting device, a metal plate made of aluminum is provided with a projection that protrudes forward, and a housing recess is formed on the front side of the projection. The housing recess has a semiconductor light emitting element mounted on a bottom surface thereof. The LED element is thermally coupled to the metal plate. A printed circuit board made of a glass epoxy substrate is joined to the front surface of the metal plate. Meanwhile, a LED-mounting printed board for mounting a LED is proposed which allows manufacturing an illumination light source having excellent heat dissipation properties while receiving less heat deterioration even with increased light emission intensity (see Patent Document 2, for example). In the LED-mounting printed board, a wiring pattern to be electrically connected to a LED is provided on one side of an insulating layer, and a heat dissipation metal layer for releasing heat generated from the LED is provided on the other side of the insulating layer. A LED-mounting concave portion is formed to penetrate the insulating layer from the side of the wiring pattern and reach inside of the heat dissipation metal layer.
Further, there is proposed a light emitting device having excellent light extraction efficiency, color temperature, and color rendering index and having favorable radiant intensity of emitted light (see Patent Document 3, for example). The light emitting device includes: a base in which a mounting portion for mounting a light emitting element is formed on an upper surface thereof; a frame-shaped reflective member joined to an outer peripheral portion on the upper surface of the base so as to surround the mounting portion and provided with an inner peripheral surface serving as a reflecting surface to reflect light emitted from the light emitting element; the light emitting element mounted on the mounting portion; and a translucent member made of resin which has viscosity before hardening in a range from 0.4 Pa·s to 50 Pa·s and contains a phosphor having density in a range from 3.8 g/cm3 to 7.3 g/cm3 which converts wavelength of the light emitted from the light emitting element.
However, in the light emitting diode module according to the invention of Patent Document 1, since the printed board is attached to the front surface of the surfaces thereof, the heat generated from the element is transmitted to the metal plate and is further dissipated by using the front surface via the printed board having low heat conductivity. Hence there is a drawback that heat dissipation from the front surface cannot be effectively performed.
Meanwhile, an invention is also proposed such as the invention of Patent Document 2 or 3 in which the concave portion is formed and the light emitting diode chip is bonded in the concave portion for effectively using light emitted from the light emitting diode chip. However, in these methods, the metal plate or the like that constitutes the base needs to have a thickness equal to or more than a height of a dent of the concave portion as the semiconductor light emitting module because of its structure or manufacturing processes. This prevents creating a lightweight semiconductor light emitting module.
An object of the present invention is to provide a semiconductor light emitting module and a method of manufacturing the same, which allow maintaining higher reflectivity, obtaining uniform white light, achieving high luminance light emission by improving light extraction efficiency, while having lightweight and thin features.
Patent Document 1: Japanese Patent Laid-Open No. 2003-152225
Patent Document 2: Japanese Patent Laid-Open No. 2005-243744
Patent Document 3: Japanese Patent Laid-Open No. 2005-277331